« March 2007 | Main | May 2007 »
I thought it was wonderful to see "American Idol" perform a charity broadcast. So far over 60 million dollars have been raised for charities in the US and in Africa. 60 million dollars! Wow, that's a lot of money to come from one great idea. I donated some money online to do my part. You can find out more about this worthy effort at: www.americanidol.com/idolgivesback.
As mentioned before, body fat levels are the same for sprinters/runners from a competitive distance of 100 meters up to 10,000 meters. Yet looking at the physiques of sprinters versus distance runners, you do see one main difference: muscle mass. Sprinters are generally more muscular, and as distances increase you generally see the amount of muscle mass decline. This makes sense, as more muscle is needed to produce speed for short sprints, and less muscle mass(but more muscle endurance) is needed for the slower speeds of distance running.
I thought it would be interesting to find out if this relationship of distance versus muscle mass held up through the aging process. Using two separate papers (one and two), I was able to compare older endurance runners versus older sprinters.
I chose to compare the body composition for the 60-69 age range. Here is the comparison:
| Height(cm) | Weight(kg) | Body Fat (%) | |
| Sprinters | 172.7 | 71.2 | 13.6 |
| Endurance Runners | 171 | 66.7 | 14 |
Body fat levels between the two groups are similar, but you can see the big difference is in total weight. Sprinters weigh about 10 pounds more than the endurance runners. Given the similar levels of body fat, you have to conclude that this difference is primarily muscle mass.
There could be some self-selection here, with individuals who are naturally more muscular choosing sprinting instead of distance running. There's no way to tell for sure with these studies since they are cross-sectional analyses. But my bet is that sprint training leads to increased muscle mass and maintenance of this muscle mass across the lifespan.
After reflecting on the information in my previous post about runners and body fat, I think it's very intriguing that runners have similar body fat levels regardless of their main competitive distance (except for marathoners). I had previously thought that the distance itself mattered more in terms of body fat, but I guess it's simply the large volume of training needed to compete at the top level that leads to lower body fat.
The competitive distance that one trains for can have different impacts on other outcomes. I've mentioned before that sprinters have higher testosterone levels than average, and endurance athletes have lower testosterone than average. But I think the most obvious difference that a training distance can have on an outcome is muscle mass, as I will explore in the next post.
I frequently refer to two studies by led by Robert Ross that look at aerobic exercise and weight loss. For me, these two studies are benchmarks that can used to compare other exercise programs and weight loss. So far, I haven't found anything that really comes close to these two studies as far as total weight loss. One note of caution: the subjects did lose a small amount of lean mass in these studies, but this could have easily been prevented by performing a small amount of weightlifting such as one session per week. In other words, I don't think a program of solely aerobic exercise is the best, but I think these two studies show it is very effective.
Here are the two studies in pdf format. They are both freely available online, so I think it's okay for me to put them up here: Study 1(pdf) and Study 2(pdf).
I read an article in the newspaper about a new book by Jim Karas, "The Cardio-Free Diet". In this piece by ABC News, Karas states that, "cardiovascular exercise kills a weight-loss plan, your internal organs, your immune system, your time and your motivation. If your true goal is to lose weight, interval strength training is the only way to go."
Wow, cardio kills your internal organs and your immune system? That's a new one. Of course, he's getting this from the few outliers who perform too much aerobic exercise, like marathoners. But the idea that appropriate cardio "kills" is a joke; it's just some marketing hype to help him sell books.
And what's so great about interval weight training? It's certainly a sound technique, but circuit training has been around since the 1960s. I am unaware of any studies that show huge weight losses with circuit training. Compared to this study by Ross et al, 60 minutes of daily aerobic exercise without dietary restriction led to a weight loss of about a pound per week.
And if "interval strength training" is so effective, then why wouldn't plain old (aerobic) interval training be just as effective for losing weight? The reality is that interval strength training can be effective for losing weight only because it mirrors aerobic interval training. In other words, it's the process of engaging major muscle groups at high-intensity for a brief time, resting, and then repeating that burns calories. This is what can lead to some weight loss - not the fact that the intervals used are strength training intervals.
Also, the idea that we are made for a cardio-free life has no bearing to our evolutionary past. How would a hunter acquire any game by sitting in one spot and by performing something resembling interval strength training? The short answer: he wouldn't. Hunting means locomotion - getting out there walking, sprinting, and chasing game. Not lifting rocks and waiting for food to magically appear.
I recommend taking a pass on this book. The time spent reading it would be better spent performing aerobic exercise!
Running can create a lot of health benefits, but too much running has its problems. For men, there is the drop in testosterone and disruption of reproductive functions that can occur with high mileage. So how much mileage is "too much" in running?
One older study that looked at this compared high mileage runners (~60 mpw) to moderate mileage runners (~30 miles per week) to sedentary controls. The study showed that the high mileage runners had significant sperm count and motility problems as compared to the other two groups.
This study showed that runners training for a marathon had reduced sperm motility and morphology. This study says that beyond 80 minutes of running, the body switches to a "more catabolic environment".
This study supports the idea of a "volume threshold effect" for endurance running. I am working on getting the full-text of this study to see what their recommendations. In the meantime, it seems that a maximum of 30 miles per week, and a maximum of 80 minutes on an individual run, may be good ceilings to keep in mind.
Here's a study that looks at the body fat levels of top runners. From distances ranging from 100 meters to 10,000 meters, there was no difference in body fat measurements. Only for marathoners was fat mass less compared to other distances. The article mentions that this is due to the fact that success at the marathon depends heavily on fat metabolism.
I've read from various fitness gurus that when a person builds muscle, they will then burn additional bodyfat. In other words, gaining muscle is a tool for fat-loss, at least in the long run. The idea is that adding muscle increases your resting metabolic rate, and therefore more calories are burned during each day.
This argument falls flat for me for a number of reasons. First, it's often quoted that a newly added pound of muscle will burn anywhere from 30 to 50 extra calories per day. Yet this is not true. Christian Finn does a good job in this article showing that adding a pound of muscle will really only increase your metabolic rate by about 5 calories.
Second, you can go to any gym in America and see a heavily-muscled person with too much bodyfat. If adding muscle is the key to getting lean, then this shouldn't be happening. If you take this argument to its logical conclusion, then bodybuilders, the individuals with the most muscle out of anyone, should be ripped to the bone. Of course, bodybuilders do get lean for contests but this condition is achieved with dieting and aerobic exercise. Many bodybuilders gain 30 pounds or more in the offseason, in spite of their large amount of muscle.
Third, even if gaining muscle does increase the metabolic rate, this does not mean a person will run a calorie deficit each day. Hunger guides energy intake to make sure the body gets enough fuel for various functions, including maintaning lean mass (given the cue of intense exercise). So even if the metabolic rate is increased, a person may naturally end up eating slightly more calories each day to offset this boost in metabolic rate.
A variation of this whole argument I would buy is that maintaining muscle as a person ages helps to stop the gain of fat associated with aging. Maintaining muscle can keep resting metabolism stable throughout aging, so that if energy intake remains the same then a person won't gain weight. But the idea that if a person adds new muscle they will "burn fat all day long" is a myth.
I've seen in the news lately that autism rates among children are sharply increasing. A recent federal study estimates that now roughly 1 in every 150 children is autistic. So what's causing all this?
Some researchers believe that gluten and casein in modern diets are to blame. But a new study suggests that a lack of omega-3 fatty acids may be a large part of the problem. This new randomized, double-blind study showed that supplementation with omega-3 fatty acids significantly reduced symptoms in autistic children.
I hope that additional studies on this continue and that this information becomes more available to the public. Many modern conditions can at least be partially treated by reverting to a Paleolithic diet. In my opinion, this should usually be the first line of treatment before more drastic measures are taken.
Speaking of heart rates, here's a website for "Heart Math", a non-profit group that researches heart rates and their effects on health. They also have a for-profit division, www.heartmath.com, where they sell different products and services.
I came across the Heart Math websites years ago, but I still can't make up my mind about them. I think their general idea is right, but I just don't know if there's enough evidence to support their claims. Maybe someone else out there has a better perspective on this organization.
